But now an effort to resurrect the bank, led by Democrats and business-backed Republicans, could trigger open warfare within the GOP. And the battle over Ex-Im could upend a must-pass highway bill that lawmakers are scrambling to pass before the end of the month.

Conservatives aren’t going to go quietly, and GOP leaders would likely risk the wrath of the right if they chose to let an Ex-Im renewal advance.

“I think our leadership understands where Republicans in the House are on this issue,” said Rep. Bill Flores of Texas, chairman of the Republican Study Committee. “They don’t want Ex-Im reauthorized.”

Bank supporters, including nearly all Democrats and many moderate Republicans, will get their chance to challenge the conservative wing as early as this week, when the Senate is expected to take up the highway bill. Because it’s a must-pass measure, Export-Import backers have targeted it as a quick way to send a bank reauthorization to President Barack Obama’s desk.

“Not having the Ex-Im Bank authorized today is costing us business,” Sen. Heidi Heitkamp (D-N.D.) said. “Every day we’re not in business — where we can’t take an application or guarantee a credit — are days that we’re hurting American workers, and so we need to do everything we can to reauthorize it this month.”

A clear majority of both the House and Senate support the Export-Import Bank, whose charter expired last month and rendered the agency unable to underwrite any new loans. Sixty House Republicans have publicly supported the bank, and 180 House Democrats are on record backing the agency.

Meanwhile, 65 senators, including 22 Republicans, voted in favor of the bank in a key test vote in June. But a majority of Senate Republicans, including its top four leaders, voted against the bank in that key vote, and conservative forces both on and off Capitol Hill believe a majority of the House GOP oppose it as well. At least 95 House Republicans have indicated publicly that they won’t support the bank.

Conservative lawmakers are already crowing about Ex-Im’s demise, pointing to it as one of the first and biggest successes of the new GOP-controlled Congress.

House conservatives are pledging to keep up opposition to the bank even as the Senate works toward reauthorization. The majority of these hard-line members are opposed to any highway deal that would reauthorize the bank’s charter and have indicated to GOP leadership not to count on their votes — which could force Speaker John Boehner (R-Ohio), who has praised the bank as essential to job growth, to turn to House Democrats for votes on a final highway package.

Boehner has tried to strike a delicate balance with his conservative members. He’s told Financial Services Chairman Jeb Hensarling that if the Senate sends over a highway bill with Ex-Im measures attached, the Texas Republican will be allowed to offer amendments to the bill. That would put pressure on Hensarling to whip enough Republicans against the bank to ensure its charter is not renewed.

In the Senate, Majority Leader Mitch McConnell (R-Ky.) is open to amendments on the highway bill and expects Ex-Im backers to offer one. He’s likely to face pressure from conservatives like Sen. Ted Cruz (R-Texas) — who’s threatened to use any procedural weapon in his arsenal on the highway bill to ensure the bank stays dead — to shut down any prospects of a bank reauthorization.

But with at least 65 votes already on record in favor of the bank, it would be politically impossible for McConnell — who has made a more open and freewheeling chamber a key tenet of his tenure so far as majority leader — to block a vote.

Even on its own, the politics of the underlying highway bill are complicated.

House and Senate Republicans are colliding over how to get a bill to Obama that keeps money flowing for rundown roads and bridges in need of repair by the end of the month, when the Highway Trust Fund is expected to run dry.

House Republicans, backed by more than 130 Democrats, easily cleared a bill that fuels the trust fund with enough cash to keep it running until December. But Senate Republicans want a highway bill that runs at least through the November 2016 elections.

And the main problem for Senate Republicans: They haven’t even released a bill.

A key test vote on a highway measure is set for Tuesday afternoon in the Senate, but Democrats haven’t said whether they’ll help advance it since the bill isn’t finished. Senators are still tussling over how to pay for the highway measure, and offsets that are too far to the right could turn off Democrats — who’ll likely be needed to get the bill across the finish line.

Sen. Jim Inhofe (R-Okla.), chairman of the Senate Environment and Public Works Committee and an opponent of Ex-Im, said if a reauthorization were attached, the highway bill could lose some votes once it heads over to the House.

“I think we have enough votes over there anyway,” Inhofe said. “But it wouldn’t do it any good.”

And that dynamic is just what Ex-Im backers fear.

“My concern is not having enough for Ex-Im,” Heitkamp said. “It’s whether the vehicle, the debate about surface transportation will in fact create some concerns for people so they might vote for the amendment, but not be able to vote for the bill.”

The Ex-Im language that supporters will try to get included in the highway bill hews closely to a bill written by Heitkamp and Mark Kirk (R-Ill.), two of the Senate’s most vocal proponents of the export agency. It would reauthorize the bank’s charter for four years.

And adding to the jumbled politics of the highway bill, Sen. Rand Paul (R-Ky.) last week threw another curveball: The 2016 hopeful is threatening to use procedural tactics to force a vote on defunding Planned Parenthood. The highway bill, work on which is likely going to run into next week, is a ripe target for Paul.

House Republicans want no part of the Senate highway mess, and some of the House’s influential members are pushing senators to swallow their short-term highway fix and veer clear of attaching any Ex-Im reauthorizations.

When the five-month highway patch passed last week, House Ways and Means Committee Chairman Paul Ryan (R-Wis.) — who wants the short-term bill to buy time for a broader, multiyear highway measure — urged senators to quickly pass it, “without any unrelated measures.”

Still, if Boehner were to move to put a Senate compromise bill to the floor, it would face stiff opposition from the House Freedom Caucus and even some more moderate members, including Majority Leader Kevin McCarthy (R-Calif.). And while Boehner has turned to House Minority Leader Nancy Pelosi before for “yes” votes, he has faced harsh criticism each time.

“Six months ago, if I was to tell any of you that we’d be 15 days into July and the Export-Import Bank would not be reauthorized, you all would have laughed at me,” said Rep. Jim Jordan (R-Ohio), chairman of the House Freedom Caucus, last week. “But that’s exactly where we are at. Momentum, I think, is on our side.”